Portion of a shoe midsole



FIG. 1 is a front perspective view of a portion of a shoe midsole showing my new design;

FIG. 2 is a rear perspective view thereof;

FIG. 3 is a side view thereof; and,

FIG. 4 is a bottom view thereof.

The broken line showing of the remainder of the shoe is for illustrative purposes only and forms no part of the claimed design. 

The ornamental design for a portion of a shoe midsole, as shown and described. 